Table of Contents
BEST IELTS General Reading Test 497
IELTS GENERAL READING TEST 497 – PASSAGE – 3
IELTS GENERAL READING TEST – 497
READING PASSAGE – 3
Bacteriophages
A viral solution to antibiotic resistance?
The use of antibiotics has entered a crisis stage. More and more antibiotic resistant bacteria are emerging that cannot be cured if the body’s own immune system cannot defeat them. It can take scientists decades to come up with a new antibiotic and get government approval. This means medicine is fighting a losing battle as bacteria are increasingly evolving to resist antibiotics. An alternative method to fight these infections might be through bacteriophages, which are viruses that prey on bacteria.
Bacteriophages, or phages, were discovered more than ten years before penicillin, and it was found they could successfully treat cholera and dysentery, though it was not well understood why at the time. Scientists observed that there was a section of the population that recovered from these illnesses independently and they hypothesized that they had developed some way of fighting bacteria in their intestinal tract. Faeces samples were taken from these patients and transferred into other patients. In one early study in India, the majority of people with cholera who were untreated died, while those treated with phages had a 90 per cent recovery rate.
IELTS General Reading Test
Even with this early success, phage therapy was soon forgotten when penicillin was discovered by Alexander Fleming in 1928, and antibiotics became the sole focus in the fight against bacterial infections. Perhaps one of the reasons for this was that it was not until the middle of the century that phages were first observed with an electron microscope. Before that, they were barely understood, and though used in the treatment of cholera and dysentery, scientists could only speculate as to why they had been successful.
Now it is understood that phages are types of viruses that exclusively infect bacteria. Like all viruses, they reproduce by invading a host cell, replicate themselves by taking over the host cell’s mechanisms and then when leaving the cell, tend to destroy it. This can be disastrous when human cells are infected by viruses, but in the case of phages, they only attack bacteria.
IELTS General Reading Test
A phage begins its attack on bacteria by inserting its genetic material into its host, literally taking over the host’s functions. Then the phage duplicates itself multiple times. In the final stage, the phage breaks the cell walls of the bacterial host with toxic chemicals, releasing duplicates of itself to infect more bacteria. An antibiotic kills bacteria by interfering with one or more of the processes that bacteria need to survive. As these processes are similar in many bacteria, antibiotics can kill many species of bacteria at once. While antibiotics have transformed medicine by being very effective in stopping bacterial infections, the introduction of phage therapy could have numerous advantages over antibiotics.
Each type of phage only attacks one species of bacteria and so does not damage the good bacteria living in our intestinal tracts, called the gut microbiota or the gut biome. Each human body is populated by hundreds of microbe species, which have important functions in the body such as making nutrients the body is unable to create, controlling metabolism and protecting the gut lining. When antibiotics kill all the bacteria they come in contact with, it disrupts the delicate balance of the gut biome because beneficial gut bacteria are also killed.
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Bacteria does not become resistant to phages like it does to antibiotics. This is because antibiotics disturb the cellular process of bacteria, while phages destroy the cells themselves. Something that is destroyed is no longer able to develop resistance. Bacteria are also able to develop a protective biofilm that can protect them from antibiotics, but phages are equipped with tools that can digest it.
So why are phages not being used instead of antibiotics? The main reason is that because antibiotics have been so successful since their development, there has been little incentive to continue research on phage therapy. There are also some limitations to phages as well. Live phages can be difficult to isolate, and if the separation from surrounding matter is not completely clean, a deadly immune response in the patient could result. In addition, phage therapy takes longer than antibiotic treatment.
IELTS General Reading Test
Due to antibiotics universally killing all bacteria, doctors can prescribe a broad spectrum antibiotic without knowing what the offending bacteria is. In the case of phages, the bacteria not only needs to be identified, but if there is currently no known phage to treat the bacteria in question, a new one has to be found. This is why phage therapy currently tends to be used for chronic bacterial infections, rather than critical, immediately life-threatening cases.
As the search for new phages continues, and more and more are added to the arsenal, before long there should be a wide enough variety of different phages discovered to combat most bacteria. Currently, it is mainly being used as a last resort for patients with antibiotic-resistant bacterial infections. As antibiotic resistance increases, phage therapy should come into its own as a leading form of treatment.
IELTS General Reading Test
Questions 27-32
Do the following statements agree with the views of the writer in Reading Passage 3?
In boxes 27-32 on your answer sheet write
YES – if the statement agrees with the views of the writer
NO – if the statement contradicts the views of the writer
NOT GIVEN – if it is impossible to say what the writer thinks about this
27. It is impossible for medicine to keep up with the emergence of new antibiotic resistant bacteria.
28. Penicillin became the dominant treatment because early usage of phages was unsuccessful.
29. Phages were only able to be used after the invention of the electron microscope.
30. The gut biome communicates with both the nervous and digestive systems.
31. Antibiotic therapy is faster than phage therapy because the antibiotic has already been formulated.
32. It is doubtful that phage use will overtake that of antibiotics.
IELTS General Reading Test
Questions 33-37
Choose the correct letter, A, B, C or D.
33. According to the writer, antibiotics use is at a critical stage because
A. governments won’t approve new strains.
B. people’s immune systems have started attacking them.
C. they can’t be used against resistant bacteria.
D. they will be displaced by bacteriophages.
34. What was an observation made by scientists about the use of phages?
A. They were created by the body.
B. They existed in patients who had recovered from illness.
C. They were caused by illness.
D. They would only be successful in cholera patients.
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35. The writer believes that phage therapy may have been ignored because
A. no one actually saw phages until the middle of last century.
B. it was thought they were a type of bacteria.
C. the use of viruses was considered dangerous.
D. they had not been effective.
36. Scientist now know that phages
A. reproduce by taking over bacterial cells.
B. do not contain their own DNA.
C. can be destroyed with toxic chemicals
D. kill bacteria in an identical process to antibiotics.
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37. What point does the writer make about the gut biota?
A. it is not affected by antibiotics.
B. it can be damaged by phages.
C. it is the cause of antibiotic resistance.
D. it is barely affected by phages.
Questions 38-40
Complete each sentence with the correct ending, A-G, below.
Write the correct letter, A-G, in boxes 38-40 on your answer sheet.
38. Bacteria does not become resistant to phages because
39. Phages have been known to be dangerous because
40. Phages have not been used until now because
IELTS General Reading Test
A. antibiotics have been so successful they are unnecessary.
B. a bacterial cell cannot develop resistance if it has been destroyed.
C. they are only effective if the immune system is weak.
D. they can cause an immune reaction if not prepared correctly.
E. their long-term effects are unknown.
IELTS General Reading Test
IELTS General Reading Test
ANSWERS
27. YES
28. NO
29. NO
30. NOT GIVEN
31. YES
32. NO
33. C
34. B
35. A
36. A
37. D
38. B
39. D
40. A
IELTS General Reading Test